New questions are being raised surrounding the murder of Chandra Levy, the case that rocked official Washington and much of the nation in the summer of 2001 because of allegations she had been having an affair with then-Rep. Gary Condit (D-Calif.).

Closed hearings have been held to review information that may impeach the credibility of a witness who testified at the trial of Ingmar Guandique. In 2010, nearly a decade after Levy disappeared, Guandique was convicted of murdering her. He was already in prison for other crimes, and was sentenced to 60 years in prison in Levy's death. Now a case largely built on circumstantial evidence and witness testimony appears to be facing serious questions.

Prosecutors and defense attorneys have taken part in two closed hearings described as so sensitive that Levy's parents have not been told precisely what they are about. Her parents, Susan and Robert Levy have been advised of the hearings by the U.S. Attorney, but they are not being told any details about which witness may be implicated by new information. In a telephone interview with ABC News, Susan Levy said, "I'm not going to get my daughter back. I only want them to have the right person in prison."

In an interview with ABC's San Francisco station, KGO-TV, the Levys said most of their information comes from news reports.

One clue came in a December statement from the judge overseeing the case, just before the proceedings were ordered closed to the public.

"The hearing addresses issues about information that has come to the government's attention that may provide impeachment about one of its witnesses at trial, and the possible disclosure of that information may create safety issues that I have concluded are somewhat substantial here," D.C. Superior Court Judge Gerald Fisher said during a brief public portion of a Dec. 18 hearing, according to McClatchy reporter Michael Doyle, who was in the hearing room.

Because there was little to no physical evidence in Levy's death, the case against Ingmar Guandique was largely built on the testimony of witnesses, including that of an inmate, Armando Morales, who claimed Guandique told him he killed Levy. If Morales' testimony is untrue, the whole case could fall apart. But at this time it is unclear if Morales is the witness in question. The Justice Department is required to notify the court about any information raising questions about the credibility of its witnesses.